In many cellular communications systems, repeaters are used to enhance the communications channel between a controlling node of a cell and one or more users in the cell. In its simplest form, a repeater receives an incoming signal, amplifies it, and then forwards it towards a receiving party. A repeater will thus have at least two antenna beams, one for the incoming signal and one for the forwarded signal.
A repeater is a component which is usually installed on roof tops, walls, masts, etc. However, in order for the repeater to function properly, it is important that the repeater has a good channel to the transmitting party whose signals the repeater receives, amplifies and forwards. A good channel is ensured by letting the repeater's antenna beam for the incoming signal point towards the signal source, i.e. the transmitting party, in such a manner that, for example, Line-Of-Sight, LOS, is obtained.
If the repeater has a poor channel to the transmitting party, the repeater will not contribute to improved system performance. In fact, a poorly installed repeater might add more interference to the system, and thus even degrade the system performance.
Another factor which might cause degradation of system performance when a repeater is used is that the repeater will also amplify and forward any interfering signals which it receives.